Process for the continuous or intermittent vacuum distillation of mineral oils



AprilI 5, 1932. M. GENsEcKE 1,852,205

PROCESS FOR THE CONTINUOUS 0R INTERMITTENT VACUUM DISTILLTION OF MINERAL OILS .Filed Feb. 24, 1928 3 Sheets-Sheet l Q i l sa Q n .pq 0

u Au a mes/am' MPa/es RIJ/IUE /n venta/n' April 5, 1932.

Fig. 2.

M. GENSECKE PROCESS FOR THE CONTINUOUS OR' INTERMITTENT Ap 5, 1932. l M. GENsEcKE PROCESS FOR THE CONTINUOUS OR INTERMITTENT VACUUM DISTILLATION OF MINERAL OILS .3 Sheets-Sheet 3 Filed Feb. 24, 1928 Patented Apr. i932 UNITED resaca MAX GENSECKE, OF FRANKFORT-ON-THE-MAIN, GERMANY PROCESS PDB THE CONTINUOUS R INTEBMITTENT VACUUM IOISTILLATION OF MINERAL OILS Application led February 24, 1928, Serial No.- 256,750, and in Germany December 3, 1926.

This invention relates to a process for the continuous or intermittent vacuum distillation of mineral oils. A

The splitting up of mineral oils into the usual commercial fractions is frequently cffected by means of vacuum distillation. This distillation is generally performed by heating the mineral oil in a plurality of stills arranged in serial order, in relation to the direction of flow of the oil; such stills being for example often constructed in the form of a Cornish boiler. The evolved oil vapours are led from each still into a condensing apparatus which, in conjunction with an air pump, maintains a negative pressure in the, plant, equivalent,

only at the surface of this layer, the same degree of vacuum being employed.

The beneficial effect of the new process can be explained by the fact that in' the usual processes, a suiiicient intermingling of the oil in the still cannot be obtained, in spite of the introduction of steam. If, however, according to the presentinvention, lthe oil is kept in motion in the still, by means of a suitable conveying device, in suchv a manner that a mist of oil is continuously formed in the space above the liquid level, the mixing is naturally rendered far more intimate, especially if care be taken to ensure that the circulation of the oil is most intensive in the vicinity of the heating surfaces. This circulating movement of the oil however affords also another very essential advantage.

In the known processes, the formation of oil vapour can only start in the vicinity of the heating surface. Above these there was generally a column of oil of l1.5-0.7 metres high,

formation of the oil vapour is transferred to the thin films of oil produced above the li uid level in the still, whilst the heating sur ace merely effects the heating of the oil, and no longer causes the formation of the oil vapour. In contradistinction to the known processes,

' the oil vapours are produced under a uniform pressure which corresponds to the vacuum Ipresent inthe still.

Moreover by the introduction of the steam into the still, the pressure under which the formation of the oil vapour proceeds can be considerably reduced. This auxiliary steam 1s preferably employed simultaneously for the production of the thin films of oil, for example by conveyingI the oil in the still by means of this steam according to the principle of air-lift pump applied to liquids. The vacuum in the still can be further increased by forcing the aforesaid conveying steam or other auxiliary steam (after it has been freed from the oil vapours) into the steam condenser by means of conveying devices which produce an increase of pressure, (for example steam injectors).4

Tn this case also, the vacuum in the steam condenser is that determined by the temperature of the cooling water.

The vacuum on the suction side of the steam injector apparatus, that is, in the oil-condensing plant and in the still, is however increased in accordance with the adjustment of the steam injector apparatus.

This embodiment of the invention is also advantageous in those cases in which the oil is not heated in stills but in tubular coils or the like and is evaporated in thin layers after distribution.

Thus it is possible, by this invention, to carry out the distillation under a higher vacuum than 'was hitherto attainable, and to reduce the distillation temperature correspondtion of steam into the oil under treatment to such an extent that the partial pressure of the oil vapours formed at the deepest points of the still was, for example, not more than the' equivalent of l() mm. of mercury. This procedlire however, entailed using such largel amounts of'steam that thedistillation became uneconomical as soon as the vacuum was reduced to below mm. of mercury.

l In carrying outthe present invention, it is preferable. to employ a still of such construction that the oil is raised to a high level and allowed to trickle down over heating surfaces arranged above the oil level; or the heating surfaces are placed in the oil and the heated oil is raised, allowed to run down plates on which the formation of the oil vapour takes lace, and returned to the heating surfaces. uch agitating devices produce an exceedingly active circulation, so that the oil cannot burn or become superheated. Experience has shown that the amount of steam for this agitation, including the steam for operating the injector apparatus producing the high vacuum, amounts to only a fraction of the amount of distilling steam employed at present for reducing the partial pressure.

If, however, it is desired to economize with regard to the steam required for the agitating apparatus, the oilcan be agitated by other devices, such, for example, as centrifugal pumps and the like, which punips are preferably disposed outside the still. The most favourable arrangement from the economical point is to couple these agitating pumps direct to steam turbines, which for example expand the steam from atmospheres down to about v10 atmospheres the steam at this pressure being admitted to the injecting apparatus for producing the'high vacuum in the still. Y

' The invention will hereinafter be more fully explained with reference to the accompanying drawings in which Figs. 1 to 3 illustrate the methods of connecting up the parts in various embodiments of the invention. 1 f

A In all the figures of the drawings al, a2, as,

- cation with the dephlegmators or oil condenstabs,...

ers 01 c2, c3 by means of the conduits b1, The distilling or conveying steam is admitted to the stills through the conduits d1, d2, d3; Closing and regulating valves are provided in the conduits b1, b2,

. indicate stills which are in communithe oil level. One or more agitating pumps, consisting of the upcast pipes g1, g3 into whichthe steam is introduced at h1, Il. and which may be provided at their upper ends with distributors 1, 3, liftthe oil which is thereby uniformly distributed over the heating surfaces byI means of the bailles k1, las downwhich it runs inyorder to be. circulated anew. The preferred heatin agent in this case consists of superheate steam. The apparatus a2 -is constructed as a flame-tube boiler, to be heated by flue gases. The agltating devices are arranged on both sides of the heating tubes, but, in other respects the design is similarto that of the stills a1, a3,.the ballles k2 being, however, so arranged that the oil is positively led back over the surface of the flame tubes. It is of course obvious that all stills in the same plant may beof the same construction. y

The plant is operated in the following manner: The distilled oil vapours, admixed with agitating steam, pass through the conduits b1, 62,123 into the dephlegmators or con-l densers c1, c2, 03. After deposition of the distillates in 01, c2, c3, the steam is aspirated A by the injectors Z1, Z2, Z3 (which 'are operated by live steam coming from the conduits m1, m2, ma) and is condensed in the condensers which may be of any desired construction, for example surface condensers s uch as nl, n3 or asspray condensersn2. Air is evacuated from the condensers n1, n2, n3 by means of l ordinary air pumps p1, p2, p3. Instead of the indivldual condensers a common condenser can be employed, in which case all the steam lcondensers are connected thereto. 7' is the succession and treated in each until the desired A fraction has distilled off.

The economy in steamobtained by the present process can be further increased by. effecting the distillation in the individual stages under different degrees of vacuum, thus enabling the steam which has passed through a still to be utilized as driving orconveying steam in subsequent stills after the oil vapour has been removed by condensation. The vacuum can, for example, be so adjusted that the drop in pressure between two successive apparatus is equal to the losses in flow and the level of the oil in the previous still. In this embodiment of the invention it is only-necessary to provide the last still with a steam inv jector for producing the high vacuum, as is shown diagrammatically in Fig. 2.

The working .steam is introduced into the first still al at d1, and after the oil vapours (which must naturally have a higher boiling point than water) have been separated in the condenser c1, the steamis passed through the conduit d2 into the next still a2. The absolute pressure is for example, 750 I Inn. of mercury in al, and 600 mm. in a2,

the condenser t in which the air pump u,

maintains normal vacuum; w is the live steam conduit for the injector apparatus s.

The economy of steam as compared with the embodiment illustrated in,F ig. 1 in which all stills work under a constant degree of vacuum, can also be obtained with the arrangement shown in Fig. 3. In this embodiment the steam conveyed by the steam injector apparatus o1, '02, v3 from the condenser c1, c, 03 is condensed in the condensers y. However, live steam is admitted to only one of the stills, for example, a3, through the conduit da. The mixture of steam and oil vapour passes through `the conduit b3 into the condenser c3 in which the oil vapour is condensed, and from which steam alone is aspirated by the injector apparatus '03. Part of the steam is drawn o from the collecting conduit 2 to the condenser y and another portion is admitted to the still a2. From the still a2 the vapours are passed (again under high vacuum) through the conduit b2 to the condenser c2. The steam injector v2 aspi- -rates the mixture of oil and water vapour and conveys part of the steam, as above described into the still al. The condenser y is connected with an air pump m.

For the purpose of preventing losses due to the prevalence of excessively high temperatures in the still, the heating can be eected in all embodiments for example, b means of highly superheated steamat 450 g., circulates between the heating system of the f stills and a superheater.

In addition to the above-described arrangements a series of other arrangements are possible without departing from the spirit and scope of the invention as defined in the a pended claims, so that the process can adapted to all special local conditions as well as to the condition of the oil to be distilled.

What I claim is: v

1. In a process for the vacuum distillation of mineral oils in heated stills which comprises continuously. elevating the heated oil from the lower part of the still into the vapor space of the still by means of steam, finely dividing the oil in said vapor space under a vacuum, and condensing the oil from the resulting mixture of vaporized oil and steam without any substantial condensation of the steam, the improvement which comprises maintaining the vacuum in said still by steam injecting the uncondensed steam into a condenser. Y

2. In a rocess for the vacuum distillation of minera oil in a plurality of serially arranged heated stills under successively ins which creasing degrees of vacuum which comprises continuously elevating the heated oil from the lower part of the still into the vapor space of the still by means of steam, finely dividing the oil in said vapor space under a vacuum, and condensing the oil from the resulting mixture of vaporized oil and steam without any substantial condensationl of the steam, the limprovement which comprises elevating the oil in the successive stills by means of the 7 5 uncondensed steam from the preceding still and maintaining the vacuum in said stills by steam injecting the uncondensed steam from the last still of the series into a condenser. '4 2O 3. In a process for the vacuum distillation of mineral oil in a plurality of serially arranged heated stills lunder successively inw creasing degrees of vacuum which comprises continuously elevating the heated oil from C3' the lower part of the still into the vapor space of the still by means of steam, inely dividing the oil in said vapor space under a vacuum, and condensing the oil from the resulting mixture of vaporized oil and steam without any substantial condensation of the steam,

the improvement which comprises elevating the oil in the successive stills by steam inject. ing into it at leasta portion ofthe uncondensed steam from the preceding still and 5 maintaining the l vacuum in said stills by steam injectin the uncondensed` steam from the last still o the series into a condenser.

In testimony whereof I aliix my signature.

MAX cENsEcKE. m 

